The present invention pertains to a new device for in vitro gamete and embryo culture. The present invention is an improvement of existing gamete/embryo micro drop culture dishes, which finds particular utility by providing an innovative, cost-effective, customized means for accomplishing human assisted reproductive technology procedures, i.e., in vitro oocyte insemination and in vitro oocyte and embryo culture. This device may also be suitable for use in a variety of human and non-human embryo-related work, or in any situation that requires small volumes of medium for cell or tissue culture. In the field of culture dishes and appliances, existing devices are not specifically designed for these intended uses. There is therefore a need for a culture dish or appliance which provides small concentrically spaced wells within the confines of a larger vessel (or dish) which function to hold or maintain the integrity of small drops of fluid medium, while allowing maximal exposure to the surface area for the medium.
In a typical laboratory setting, conventional dishes used for micro drop embryo culture are planar or "flat bottomed," and of a standard 60 mm diameter. When used for gamete/embryo culture application, an aqueous medium is usually placed on the bottom of this standard dish in a series of drops, to which mineral oil or other non-aqueous fluid is added until it covers or overlays the drops. When these samples are equilibrated in an incubator, the non-aqueous overlay fluid protects the aqueous medium from potentially marked changes in pH level and temperature, but still allows for slow gas exchange, which is crucial to this process. The drops of sample material usually remain attached to the standard culture dish via surface tension. However, the drops may easily be dislodged during handling of the conventional dishes. As time passes, the drops may become increasingly easy to dislodge. Care must therefore be taken in order to prevent this dislodgement from occurring. Once dislodged, the drops may reattach, but may also move to and combine with existing drops. This corrupts the samples by changing the volume of the remaining drops, and hence the conditions that were originally established. Such an eventuality introduces variability into a procedure which demands predictability and consistency.
Other conventional culture dishes which are used in other applications utilize different methods for segregating a sample from a surrounding medium. For instance, the device disclosed in U.S. Pat. No. 3,791,930 issued to Saxholm utilizes cylindrical or rectangular supporting elements which constitute self-contained units that are separate from the culture dish. These supporting elements are inserted into an aqueous or gel-like medium so that they rest flush with the bottom of the dish, while their open upper ends extend beyond the surface of the medium. These supporting elements can be selectively inserted, removed or arranged in order to accomplish a desired application. However, the supporting elements suffer from an instability problem due to their unitary structure, which is solved by the Saxholm dish through the use of magnetic metal plates which are mounted to the underside of the supporting elements, and to the base of the dish itself, the mating of which causes the supporting elements to become attached to the dish itself.